Ambulatory Blood Pressure: A Predictor of Mortality

Published - Written by James Yeh, M.D., M.P.H.

Ambulatory blood-pressure measurements allow the differentiation of variations in blood pressure that occur throughout the day. Ambulatory blood-pressure measurements have been shown to be better than clinic blood pressure measurements for confirming the presence of hypertension and as a predictor of cardiovascular outcomes. However, the predictive value of hypertension phenotypes (e.g., white-coat and masked hypertension) and diurnal variation of blood pressure on cardiovascular outcomes is uncertain.

What is this study about?

In this week’s issue of NEJM, Banegas and colleagues report the findings from a national registry-based cohort study of the association between clinic and 24-hour ambulatory blood pressure and all-cause and cardiovascular mortality. The study included 63,910 adults (mean age, 58 years; 58% male) recruited in 2004–2014 from primary care clinics in Spain. About 27% of participants had white-coat hypertension and 38% were taking more than two blood-pressure medications. Hypertension phenotypes were defined as follows: sustained hypertension (elevated clinic and 24-hour pressure), white-coat hypertension (elevated clinic and normal 24-hour pressure), masked hypertension (normal clinic and elevated 24-hour pressure), and normotension (normal clinic and normal 24-hour pressure).

What were the findings?

During a median of 4.7 years of follow-up, 3808 patients died, and 1295 of these deaths were from cardiovascular causes (440 from ischemic heart disease, 291 from stroke, and 123 from heart failure). After adjustment for various patient factors (e.g., demographics, number of antihypertensive drugs, and cardiovascular risk factors), 24-hour systolic pressure was a stronger predictor of all-cause and cardiovascular mortality (hazard ratios for both, 1.58 vs. 1.02 per 1-SD increase in pressure) than clinic systolic blood pressure. In subgroup and multivariate analyses, systolic pressure was a better predictor of all-cause and cardiovascular mortality than diastolic pressure.

Compared with normal blood pressure, masked hypertension was associated with a nearly three-fold increased risk for all-cause mortality (HR, 2.83). Sustained hypertension (HR, 1.80) and white-coat hypertension (HR, 1.79;) also were associated with increased risk for all-cause mortality. Findings were similar for cardiovascular mortality.

In an editorial, Dr. Raymond Townsend from the Perelman School of Medicine at the University of Pennsylvania states, “the ominous effect of whitecoat hypertension has been noted by others, and it is probably related to the increasing magnitude (i.e., the difference between clinic blood pressure and ambulatory blood pressure) of white-coat hypertension with age.” According to NEJM Deputy Editor Dr. John Jarcho, “This study provides strong confirmation of previous work indicating that important information is obtained from 24-hour ambulatory blood pressure monitoring that cannot be obtained from clinic blood pressure measurements alone.”

What is my take-away?

Ambulatory 24-hour blood pressure is a stronger predictor of all-cause and cardiovascular mortality than clinic blood pressure. Masked and sustained hypertension are also associated with greater mortality risk. White-coat hypertension is not a benign finding and is also associated with increased risk for mortality.

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James Yeh, MD MPH, Physician at NEJM GroupJames Yeh, MD MPH, Physician at NEJM Group